Prevent panic when despawning entities with NoAuto components

[ramirezmike]

Objective

• This prevents a panic that can occur if an entity with one of the NoAuto components is despawned.
• Fixes Despawning Entities that have a NoAutoCenterOfMass, NoAutoAngularInertia, or NoAutoMass component causes panic #607

Solution

This solution to the problem just uses the non-panicking versions of retrieving an entity from the world and inserting a component in the on_remove_no_auto_mass_property function that runs when the component is removed.

I think an argument could be made that this silently hides an issue of code trying to operate on an entity that no longer exists or that the on_remove shouldn't fire if it's happening because an entity is being despawned.